System for controlling water content and temperature of an air stream

Abstract

A system and a method for controlling water content and temperature of an air stream. Said system comprises a contact device (3) for transferring thermal energy and water vapor between a liquid desiccant (5) and the air stream (7) flowing through the contact device. The system comprises further a regeneration device (13) which can be operated in at least a first and a second mode, wherein the first mode is a desiccant regeneration mode in which water is removed from the liquid desiccant (5) and the second mode is a desiccant heating mode in which the liquid desiccant is heated to a desired temperature below boiling point. The system comprises further a control system (22) configured for controlling the regeneration device (13) to operate in the first mode when the system (1) is used for dehumidifying the air stream (7) and to operate in the second mode when the system (1) is used for humidifying the air stream.

Description

[0001] System for controlling water content and temperature of an air stream

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to a system and a method for controlling water content and temperature of an air stream by use of a liquid desiccant.

[0004] BACKGROUND

[0005] Control of water content of an air stream is for example desirable for dehumidifying the air in cold, chilled and frozen facilities, such as cold storage and warehousing. This improves the working environment and avoids damage from moisture to equipment in the facility and on the facility itself. In other environments, such as temperate rooms, there may instead be a need for humidification of the air. A typical example of the need for controlling minimum humidity levels is to avoid static discharges (ESD) in manufacturing of electronic components and PCBs.

[0006] One type of system for controlling water content of an air stream which can be used both for dehumidification and for humidification of the air stream uses a liquid desiccant for absorbing water vapor from the air or adding water vapor into the air. Often the temperature of the air stream also needs to be controlled. This can be done by separately heating the air stream after it has passed via the liquid desiccant. However, in WO2022 / 203573 it is described how both temperature and water content of the air stream can be adjusted simultaneously. There is a need to optimize capacity and energy consumption for such systems.

[0007] SUMMARY

[0008] It is an object of the present invention to provide an improved system and method for controlling water content and temperature of an air stream. This is achieved in a system for controlling water content and temperature of an air stream and in a method for controlling such a system according to the independent claims.

[0009] According to one aspect of the invention a system for controlling water content and temperature of an air stream is provided. Said system comprising:

[0010] - a contact device for transferring thermal energy and water vapor between a liquid desiccant and the air stream flowing through the contact device, said liquid desiccant flowing through the contact device from a liquid desiccant inlet to a liquid desiccant outlet and said air stream flowing through the contact device from an air stream inlet to an air stream outlet, the contact device being configured to allow a contact between the liquid desiccant and the air stream in which contact thermal energy and water vapor is transferred;

[0011] - a regeneration part connected in the system such that liquid desiccant expelled from the liquid desiccant outlet of the contact device can be circulated through the regeneration part, said regeneration part comprising a regeneration device which can be operated in at least a first and a second mode, wherein the first mode is a desiccant regeneration mode in which water is removed from the liquid desiccant and the second mode is a desiccant heating mode in which the liquid desiccant is heated to a desired temperature below boiling point; and

[0012] - a control system connected to the regeneration device, wherein said control system is configured for controlling the regeneration device to operate in the first mode when the system is used for dehumidifying the air stream and to operate in the second mode when the system is used for humidifying the air stream.

[0013] According to another aspect of the invention a method for controlling a system for controlling water content and temperature of an air stream according to the invention is provided. Said method comprises the steps of: - controlling by the control system the regeneration device to operate in a first mode which is a desiccant regeneration mode in which water is removed from the liquid desiccant, when the system is used for dehumidifying the air stream; and

[0014] - controlling by the control system the regeneration device to operate in a second mode which is a desiccant heating mode in which the liquid desiccant is heated to a desired temperature below boiling point, when the system is used for humidifying the air stream.

[0015] Hereby a system and method for controlling water content and temperature of an air stream are achieved, by which the desiccant efficiently can be tempered by use of the regeneration device when the system is used for humidification. Hereby no extra heat pump or heat exchanger needs to be provided for this purpose of heating the desiccant whereby a more compact and more easily handled system for controlling water content and temperature of an air stream is achieved. Hereby energy consumption of the system is also optimized. By raising the temperature of the liquid desiccant when the system is used for humidification the temperature of the air passing the liquid desiccant in the contact device of the system will also be raised. Hereby a temperature of the air can be controlled and can be kept at a desired level after having passed the system without the need of further devices for raising the temperature.

[0016] With a liquid desiccant of comparatively higher temperature a capacity for adding water in the humidifying process is increased. Furthermore, a temperature of the room can be maintained with use of less energy by increasing the temperature of the desiccant according to the invention.

[0017] In one embodiment of the invention the system further comprises:

[0018] - a liquid desiccant collecting tank which is positioned for receiving liquid desiccant from the liquid desiccant outlet of the contact device, said liquid desiccant collecting tank comprising a regeneration inlet, a regeneration outlet and a recirculation outlet, wherein the regeneration part is connected to the regeneration inlet and the regeneration outlet of the liquid desiccant collecting tank such that liquid desiccant expelled from the liquid desiccant outlet of the contact device can be circulated through the regeneration part from the regeneration outlet to the regeneration inlet; and

[0019] - a recirculation part connected to the recirculation outlet of the liquid desiccant collection tank such that liquid desiccant expelled from the liquid desiccant outlet of the contact device can be recirculated via the recirculation part and reintroduced to the contact device via the liquid desiccant inlet.

[0020] In one embodiment of the invention said control system is configured to control the regeneration device to operate in the first or second mode based on information received from one or more sensors provided in the system for measuring temperature and / or water content of the air stream before and / or after the air stream passes the contact device.

[0021] In one embodiment of the invention the system comprises:

[0022] - a first temperature sensor and a first water content sensor which are positioned in the system such that they can measure the temperature and the water content respectively of the air stream after the air stream has passed through the contact device, said first temperature sensor and said first water content sensor are in communication contact with said control system;

[0023] - a second temperature sensor and a second water content sensor which are positioned in the system such that they can measure the temperature and the water content respectively of the liquid desiccant to be introduced into the contact device via the liquid desiccant inlet, said second temperature sensor and said second water content sensor are in communication contact with said control system; and possibly

[0024] - a third temperature sensor and a third water content sensor which are positioned in the system such that they can measure the temperature and the water content respectively of the air stream before the air stream passes through the contact device, said third temperature sensor and said third water content sensor are in communication contact with said control system, and wherein the control system is configured to determine to which temperature the desiccant is to be heated in the regeneration device and / or at what rate the desiccant is to be pumped through the regeneration part when the regeneration device is operated in the second mode, said determination being based on information received from one or more of said first temperature sensor, first water content sensor, second temperature sensor, second water content sensor, third temperature sensor and third water content sensor, wherein said control system further is configured to control said regeneration device and / or at least one pump provided in the regeneration part according to said determination.

[0025] In one embodiment of the invention said control system is configured to determine to which temperature the desiccant is to be heated in the regeneration device and / or at what rate the desiccant is to be pumped through the regeneration part when the regeneration device is operated in the second mode such that cooling of the air stream due to the humidification provided to the air stream is compensated and possibly such that a wanted temperature increase of the air stream also is provided and wherein the control system further is configured to control the regeneration device to heat the liquid desiccant to the determined temperature and / or to control the at least one pump to pump at the determined pump rate.

[0026] In one embodiment of the invention the control system further is connected to a water adding device and is configured to control the water adding device to add water to the liquid desiccant collection tank in dependence of information received from one or more of said first temperature sensor, first water content sensor, second temperature sensor, second water content sensor, third temperature sensor and third water content sensor.

[0027] In one embodiment of the invention the regeneration device is a boiler.

[0028] In one embodiment of the invention the liquid desiccant is a salt such as Calcium Chloride, CaCh, Magnesium Chloride, MgCL , Potassium Sulfate, K2SO4 or Potassium Formate HCO2K.

[0029] In one embodiment of the invention the method further comprises the steps of: - measuring a temperature and a water content of the air stream by a first temperature sensor and a first water content sensor of the system after the air stream has passed through the contact device and possibly measuring a temperature and a water content of the air stream by a third temperature sensor and a third water content sensor of the system before the air stream has passed through the contact device;

[0030] - determining in the control system if the regeneration device is to operate in the first or the second mode based on the measured temperature and / or water content of the air stream before and / or after the air stream has passed through the contact device.

[0031] In one embodiment of the invention the method further comprises the steps of:

[0032] - determining in the control system to which temperature the desiccant is to be heated in the regeneration device and / or at what rate the desiccant is to be pumped through the regeneration part when the regeneration device is operated in the second mode, said determination being based on measured temperature and / or water content of the air stream before and / or after the air stream has passed through the contact device and / or based on a measured temperature and / or water content of the desiccant measured by a second temperature sensor and a second water content sensor provided in the system; and

[0033] - controlling by the control system the regeneration device and / or at least one pump provided in the regeneration part according to said determination when the regeneration device is operated in the second mode.

[0034] In one embodiment of the invention the step of determining in the control system to which temperature the desiccant is to be heated in the regeneration device and / or at what rate the desiccant is to be pumped through the regeneration part when the regeneration device is operated in the second mode is provided such that cooling of the air stream due to the humidification provided to the air stream is compensated and possibly such that a wanted temperature increase of the air stream also is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic drawing of a system for controlling water content and temperature of an air stream according to one example of the invention.

[0036] Figure 2 is a flow chart of a method according to one example of the invention.

[0037] DETAILED DESCRIPTION

[0038] A system for controlling water content and temperature of an air stream is disclosed. The system according to the invention uses a liquid desiccant and can be used both for dehumidification and for humidification of the air stream. The liquid desiccant absorbs water vapor from the air or adds water vapor into the air.

[0039] Figure 1 is a schematic drawing of a system 1 for controlling water content and temperature of an air stream 7 according to one example of the invention. The system 1 comprises a contact device 3 for transferring thermal energy and water vapor between a liquid desiccant 5 and the air stream 7 flowing through the contact device 3. The liquid desiccant 5 flows through the contact device 3 from a liquid desiccant inlet 9a to a liquid desiccant outlet 9b and said air stream 7 flows through the contact device from an air stream inlet 10a to an air stream outlet 10b. The air stream 7 is in this example pushed towards the air stream inlet 10a by an air fan 51 provided in the system 1. However, another alternative would be to pull the air stream through the contact device 3 by a sucking device positioned in connection with the air stream outlet 10b. The contact device 3 is configured to allow a contact between the liquid desiccant 5 and the air stream 7 in which contact thermal energy and water vapor is transferred. When the system 1 is used as a dehumidifier the liquid desiccant 5 will adsorb water vapor from the air stream 7 and when the system 1 is used as a humidifier the liquid desiccant 5 will add water vapor into the air stream 7. The system 1 comprises further suitably a liquid desiccant distributor 6 which is connected to the liquid desiccant inlet 9a and configured for distributing the liquid desiccant into the contact device 3. The system 1 comprises further suitably a liquid desiccant collecting tank 41 which is positioned for receiving liquid desiccant 5 from the liquid desiccant outlet 9b of the contact device 3. The liquid desiccant collecting tank 41 comprises a regeneration inlet 42a and a regeneration outlet 42b to which a regeneration part 11 is connected. The liquid desiccant collecting tank 41 comprises further a recirculation outlet 42c to which a recirculation part 21 is connected. The regeneration part 11 is connected to the regeneration inlet 42a and the regeneration outlet 42b of the liquid desiccant collecting tank 41 such that liquid desiccant 5 expelled from the liquid desiccant outlet 9b of the contact device 3 and collected in the liquid desiccant collection tank 41 can be circulated through the regeneration part 11 from the regeneration outlet 42b to the regeneration inlet 42a. The regeneration part 11 comprises at least one regeneration pump 17 for pumping the liquid desiccant 5 through the regeneration part 11. In the example as shown in Figure 1 two regeneration pumps 17 are provided, however only one regeneration pump 17 may be provided in another example. The regeneration part 11 comprises a regeneration device 13 for removing water from the liquid desiccant 5 when the system is used for dehumidification of the air stream 7. The regeneration device 13 can be for example a boiler or a vacuum boiler. When the system is used as dehumidifier the desiccant is treated in the regeneration device 13 such that water is removed from the liquid desiccant 5 and the temperature of the liquid desiccant 5 will increase.

[0040] The recirculation part 21 is connected to the recirculation outlet 42c of the liquid desiccant collection tank 41 such that liquid desiccant 5 expelled from the liquid desiccant outlet 9b of the contact device 3 and collected in the liquid desiccant collection tank 41 can be recirculated via the recirculation part 21 and reintroduced to the contact device 3 via the liquid desiccant inlet 9a. The recirculation part 21 comprises at least one recirculation pump 27 for pumping the liquid desiccant 5 through the recirculation part 21. A filter 28 is suitably also provided in the recirculation part 21.

[0041] In some examples, but not necessarily for the invention, the regeneration part 11 further comprises a liquid-to-liquid heat exchanger 15 via which liquid desiccant 5 is transferred both on its way to the regeneration device 13 from the liquid desiccant collecting tank 41 and from the regeneration device 13 back to the liquid desiccant collecting tank 41. Hereby heat from the regeneration process can be used for heating the liquid desiccant 5 on its way to the regeneration device 13 and hereby energy consumption can be reduced.

[0042] As discussed above in the summary, the system 1 can as well be used as a humidifier in a heated room. In that case the liquid desiccant 5 adds water vapor to the air stream 7 in the contact device 3. Hereby a water adding device 45 is needed in the system 1. The water adding device 45 is for example configured and positioned for adding water to the liquid desiccant collecting tank 41. When the system 1 is used as humidifier the regeneration part 11 is not necessary for removing water from the liquid desiccant 5. However, according to the invention the liquid desiccant 5 is still circulated through the regeneration part 11 and the liquid desiccant 5 is heated by the regeneration device 13. However, the liquid desiccant 5 should not be boiled but just heated in a controlled way. According to the invention the regeneration device 13 is controlled by a control system 22 such that the liquid desiccant 5 is heated to a suitable temperature. Hereby no other device for heating of the liquid desiccant 5 is needed. Furthermore, the liquid desiccant 5 can be heated in a controlled way such that no further heating of the air stream 7 is needed. Hereby a suitable control of both humidity and temperature of the air stream 7 is achieved according to the invention.

[0043] According to the invention the regeneration part 11 comprises a regeneration device 13 which can be operated in at least a first and a second mode, wherein the first mode is a desiccant regeneration mode in which water is removed from the liquid desiccant 5 and the second mode is a desiccant heating mode in which the liquid desiccant is heated to a desired temperature below boiling point. The system 1 comprises further a control system 22 connected to the regeneration device 13, wherein said control system 22 is configured for controlling the regeneration device 13 to operate in the first mode when the system 1 is used for dehumidifying the air stream 7 and to operate in the second mode when the system 1 is used for humidifying the air stream 7. In the example of the system 1 as shown in Figure 1 a number of sensors 24a, 24b, 25a, 25b, 26a, 26b are provided in the system 1. The number and position of sensors can be varied. A first temperature sensor 24a and a first water content sensor 24b may be positioned in the system 1 such that they can measure the temperature and the water content respectively of the air stream 7 after the air stream 7 has passed through the contact device 3. The first temperature sensor 24a and the first water content sensor 24b could also be combined into one and the same sensor device. The first temperature sensor 24a and said first water content sensor 24b are in communication contact with said control system 22.

[0044] A second temperature sensor 25 a and a second water content sensor 25b may be positioned in the system 1 such that they can measure the temperature and the water content respectively of the liquid desiccant 5 to be introduced into the contact device 3 via the liquid desiccant inlet 9a. Hereby the second temperature sensor 25a and the second water content sensor 25b (which also can be combined into one sensor device) may be positioned somewhere in a fluid line of the recirculation part 21 as shown in Figure 1. However, the second temperature sensor 25a and the second water content sensor 25b may instead be positioned in the desiccant collecting tank 41. The second temperature sensor 25 a and said second water content sensor 25b are in communication contact with said control system 22.

[0045] The system 1 may also comprise a third temperature sensor 26a and a third water content sensor 26b (which may be combined into one sensor device) which are positioned in the system 1 such that they can measure the temperature and the water content respectively of the air stream 7 before the air stream 7 passes through the contact device 3 as shown in Figure 1. The third temperature sensor 26a and the third water content sensor 26b are in communication contact with said control system 22.

[0046] The control system 22 may be configured to control the regeneration device 13 to operate in the first or second mode based on information received from one or more of the sensors 24a, 24b, 26a, 26c provided in the system 1 for measuring temperature and / or water content of the air stream 7 before and / or after the air stream passes the contact device 3. Hereby a threshold temperature and / or a threshold water content can be set above or below which the operation mode of the regeneration device 13 should be changed. Such a threshold temperature and / or water content can be set in the control system 22 and the control system 22 can be configured to compare measured temperatures and / or water content of the air stream 7 as received from one or more of the sensors 24a, 24b, 26a, 26c and to control the regeneration device 13 to operate in the first or second mode according to this.

[0047] The control system 22 may further be configured to determine to which temperature the desiccant is to be heated in the regeneration device 13 and / or at what rate the desiccant is to be pumped through the regeneration part 11 when the regeneration device is operated in the second mode. The amount of desiccant 5 which is pumped through the regeneration part 11 and hereby is heated by the regeneration device 13 can be controlled by controlling the one or more pumps 17 in the regeneration part 11 and the temperature to which the desiccant is heated can be controlled by controlling the effect of the regeneration device 13. Both these factors will affect the temperature of the desiccant 5 in the desiccant collecting tank 41 and in the recirculation part 21. This determination can be based on information received from one or more of said first temperature sensor 24a, first water content sensor 24b, second temperature sensor 25 a, second water content sensor 25b, third temperature sensor 26a and third water content sensor 26b. The control system 22 is further configured to control said regeneration device 13 and / or at least one pump 17 provided in the regeneration part 11 according to said determination.

[0048] In one example the control system 22 is configured to determine to which temperature the desiccant is to be heated in the regeneration device 13 and / or at what rate the desiccant is to be pumped through the regeneration part 11 such that a cooling of the air stream 7 provided in the contact device 3 due to the humidification of the air stream is compensated, i.e. such that the increase of temperature of the desiccant provided to the contact device 3 allows the temperature of the air stream 7 to be the same before and after having passed the contact device. If the system 1 also is used for increasing the temperature of the air stream 7 such a wanted increase of temperature of the air stream 7 can also be used by the control system 22 when determining to which temperature the desiccant is to be heated (and / or at what rate the desiccant is to be pumped through the regeneration part). The control system 22 is further configured to control the regeneration device 13 to heat the liquid desiccant to the determined temperature and / or to control the at least one pump 17 to pump at the determined pump rate.

[0049] The control system 22 is further suitably connected to the water adding device 45 and is configured to control the water adding device 45 to add water to the liquid desiccant collection tank 41 in dependence of information received from one or more of said first temperature sensor 24a, first water content sensor 24b, second temperature sensor 25a, second water content sensor 25b, third temperature sensor 26a and third water content sensor 26b.

[0050] The liquid desiccant may be a salt such as Lithium Bromide, LiBr, Calcium Chloride, CaCL, Magnesium Chloride, MgCLz, Potassium Sulfate, K2SO4 or Potassium Formate, HCO2K.

[0051] The contact device 3 may be an evaporator pad. The contact device 3 may also be a liquid to air membrane energy exchanger, LAMEE.

[0052] Hereby the system according to the invention will provide an efficient way to humidify air without cooling the air. Cooling of the air is a typical behavior of traditional prior art evaporative humidification devices and to restore temperature in such devices an additional heating element is needed in series after the humidifier. Such an additional heating element is hereby not needed in the present invention.

[0053] The present invention will also avoid many of the problems of traditional steam humidification devices where extensive installation of tubing of steam / retum lines needs to be implemented.

[0054] The system 1 can be based on a controlled vapor pressure technology, CVP, where the vapor pressure in the liquid desiccant is controlled to match desired air output quality. This is described in more detail in WO2022 / 203573.

[0055] Also according to the invention a method for controlling a system 1 for controlling water content and temperature of an air stream 7 as described above is provided. The method comprises controlling by the control system 22 the regeneration device 13 to operate in a first mode which is a desiccant regeneration mode in which water is removed from the liquid desiccant 5, when the system 1 is used for dehumidifying the air stream 7 and controlling by the control system 22 the regeneration device 13 to operate in a second mode which is a desiccant heating mode in which the liquid desiccant is heated to a desired temperature below boiling point, when the system 1 is used for humidifying the air stream 7.

[0056] A flow chart of one example of the method is shown in Figure 2 and the method steps are described below:

[0057] S 1 : Measuring a temperature and a water content of the air stream 7 by a first temperature sensor 24a and a first water content sensor 24b of the system 1 after the air stream 7 has passed through the contact device 3 and possibly measuring a temperature and a water content of the air stream 7 by a third temperature sensor 26a and a third water content sensor 26b of the system 1 before the air stream 7 has passed through the contact device 3.

[0058] S2: Determining in the control system 22 if the regeneration device 13 is to operate in the first or the second mode based on the measured temperature and / or water content of the air stream 7 before and / or after the air stream 7 has passed through the contact device 3.

[0059] S3: Controlling by the control system 22 the regeneration device 13 to operate in the first mode or the second mode in accordance with said determination.

[0060] In one example said method further comprises a step:

[0061] S4: Determining in the control system 22 to which temperature the desiccant 5 is to be heated in the regeneration device 13 and / or at what rate the desiccant 5 is to be pumped through the regeneration part 11 when the regeneration device 13 is operated in the second mode. Said determination is based on measured temperature and / or water content of the air stream 7 before and / or after the air stream 7 has passed through the contact device 3 and / or based on a measured temperature and / or water content of the desiccant 5 measured by a second temperature sensor 25a and a second water content sensor 25b provided in the system 22. Said determination may also take into account and compensate for a cooling provided to the air stream 7 due to the humidification in the contact device 3. The desiccant can also be further heated in order to provide a possible wanted temperature increase to the air stream 7. S5: Controlling by the control system 22 the regeneration device 13 and / or at least one pump 17 provided in the regeneration part 11 according to said determination when the regeneration device 13 is operated in the second mode.

Claims

CLAIMS1. A system (1) for controlling water content and temperature of an air stream (7) comprising:- a contact device (3) for transferring thermal energy and water vapor between a liquid desiccant (5) and the air stream (7) flowing through the contact device (3), said liquid desiccant flowing through the contact device (3) from a liquid desiccant inlet (9a) to a liquid desiccant outlet (9b) and said air stream (7) flowing through the contact device from an air stream inlet (10a) to an air stream outlet (10b), the contact device (3) being configured to allow a contact between the liquid desiccant (5) and the air stream (7) in which contact thermal energy and water vapor is transferred;- a regeneration part (11) connected in the system (1) such that liquid desiccant (5) expelled from the liquid desiccant outlet (9b) of the contact device (3) can be circulated through the regeneration part (11), said regeneration part (11) comprising a regeneration device (13) which can be operated in at least a first and a second mode, wherein the first mode is a desiccant regeneration mode in which water is removed from the liquid desiccant (5) and the second mode is a desiccant heating mode in which the liquid desiccant is heated to a desired temperature below boiling point; and- a control system (22) connected to the regeneration device (13), wherein said control system (22) is configured for controlling the regeneration device (13) to operate in the first mode when the system (1) is used for dehumidifying the air stream (7) and to operate in the second mode when the system (1) is used for humidifying the air stream (7).

2. System (1) according to claim 1 further comprising:- a liquid desiccant collecting tank (41) which is positioned for receiving liquid desiccant (5) from the liquid desiccant outlet (9b) of the contactdevice (3), said liquid desiccant collecting tank comprising a regeneration inlet (42a), a regeneration outlet (42b) and a recirculation outlet (42c), wherein the regeneration part (11) is connected to the regeneration inlet (42a) and the regeneration outlet (42b) of the liquid desiccant collecting tank (41) such that liquid desiccant (5) expelled from the liquid desiccant outlet (9b) of the contact device (3) can be circulated through the regeneration part (11) from the regeneration outlet (42b) to the regeneration inlet (42a); and- a recirculation part (21) connected to the recirculation outlet (42c) of the liquid desiccant collection tank (41) such that liquid desiccant (5) expelled from the liquid desiccant outlet (9b) of the contact device (3) can be recirculated via the recirculation part (21) and reintroduced to the contact device (3) via the liquid desiccant inlet (9a).

3. System according to claim 1 or 2, wherein said control system (22) is configured to control the regeneration device (13) to operate in the first or second mode based on information received from one or more sensors (24a, 24b, 26a, 26c) provided in the system (1) for measuring temperature and / or water content of the air stream (7) before and / or after the air stream passes the contact device (3).

4. System according to any one of the preceding claims, wherein the system comprises:- a first temperature sensor (24a) and a first water content sensor (24b) which are positioned in the system (1) such that they can measure the temperature and the water content respectively of the air stream (7) after the air stream (7) has passed through the contact device (3), said first temperature sensor (24a) and said first water content sensor (25 a) are in communication contact with said control system (22);- a second temperature sensor (25 a) and a second water content sensor (25b) which are positioned in the system (1) such that they can measure the temperature and the water content respectively of the liquid desiccant (5) to be introduced into the contact device (3) via the liquid desiccant inlet (9a), said second temperature sensor (25 a) and said second water content sensor (25b) are in communication contact with said control system (22); and possibly- a third temperature sensor (26a) and a third water content sensor (26b) which are positioned in the system (1) such that they can measure the temperature and the water content respectively of the air stream (7) before the air stream (7) passes through the contact device (3), said third temperature sensor (26a) and said third water content sensor (26b) are in communication contact with said control system (22), and wherein the control system (22) is configured to determine to which temperature the desiccant is to be heated in the regeneration device (13) and / or at what rate the desiccant is to be pumped through the regeneration part (11) when the regeneration device is operated in the second mode, said determination being based on information received from one or more of said first temperature sensor (24a), first water content sensor (24b), second temperature sensor (25 a), second water content sensor (25b), third temperature sensor (26a) and third water content sensor (26b), wherein said control system (22) further is configured to control said regeneration device (13) and / or at least one pump (17) provided in the regeneration part (11) according to said determination.

5. System according to claim 4, wherein said control system (22) is configured to determine to which temperature the desiccant is to be heated in the regeneration device (13) and / or at what rate the desiccant is to be pumped through the regeneration part (11) when the regeneration device is operated in the second mode such that cooling of the air stream (7) due to the humidification providedto the air stream is compensated and possibly such that a wanted temperature increase of the air stream (7) also is provided and wherein the control system (22) further is configured to control the regeneration device (13) to heat the liquid desiccant to the determined temperature and / or to control the at least one pump (17) to pump at the determined pump rate.

6. System according to claim 4 or 5, wherein the control system (22) further is connected to a water adding device (45) and is configured to control the water adding device (45) to add water to the liquid desiccant collection tank (41) in dependence of information received from one or more of said first temperature sensor (24a), first water content sensor (24b), second temperature sensor (25 a), second water content sensor (25b), third temperature sensor (26a) and third water content sensor (26b).

7. System according to any one of the preceding claims, wherein the regeneration device (13) is a boiler.

8. System according to any one of the preceding claims, wherein the liquid desiccant is a salt such as Lithium Bromide, LiBr, Calcium Chloride, CaCh, Magnesium Chloride, MgCL , Potassium Sulfate, K2SO4 or Potassium Formate HCO2K.

9. A method for controlling a system (1) for controlling water content and temperature of an air stream (7) according to any one of the preceding claims, said method comprising the steps of:- controlling by the control system (22) the regeneration device (13) to operate in a first mode which is a desiccant regeneration mode in which water is removed from the liquid desiccant (5), when the system (1) is used for dehumidifying the air stream (7); and- controlling by the control system (22) the regeneration device (13) to operate in a second mode which is a desiccant heating mode in which the liquid desiccant is heated to a desired temperature below boiling point, when the system (1) is used for humidifying the air stream (7).

10. Method according to claim 9, further comprising the steps of:- measuring a temperature and a water content of the air stream (7) by a first temperature sensor (24a) and a first water content sensor (24b) of the system (1) after the air stream (7) has passed through the contact device (3) and possibly measuring a temperature and a water content of the air stream (7) by a third temperature sensor (26a) and a third water content sensor (26b) of the system (1) before the air stream (7) has passed through the contact device (3);- determining in the control system (22) if the regeneration device (13) is to operate in the first or the second mode based on the measured temperature and / or water content of the air stream (7) before and / or after the air stream (7) has passed through the contact device (3).

11. Method according to claim 9 or 10, further comprising the steps of:- determining in the control system (22) to which temperature the desiccant (5) is to be heated in the regeneration device (13) and / or at what rate the desiccant (5) is to be pumped through the regeneration part (11) when the regeneration device (13) is operated in the second mode, said determination being based on measured temperature and / or water content of the air stream (7) before and / or after the air stream (7) has passed through the contact device (3) and / or based on a measured temperature and / or water content of the desiccant (5) measured by a second temperature sensor (25a) and a second water content sensor (25b) provided in the system (22); and- controlling by the control system (22) the regeneration device (13) and / or at least one pump (17) provided in the regeneration part (11) according to saiddetermination when the regeneration device (13) is operated in the second mode.

12. Method according to claim 11, wherein the step of determining in the control system (22) to which temperature the desiccant is to be heated in the regeneration device (13) and / or at what rate the desiccant is to be pumped through the regeneration part (11) when the regeneration device is operated in the second mode is provided such that cooling of the air stream (7) due to the humidification provided to the air stream is compensated and possibly such that a wanted temperature increase of the air stream (7) also is provided.

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